Swarming is a specialized form of bacterial motility that propels cells across a surface in a coordinated and social manner. Studied exclusively in the proteobacterial division, swarming is often a virulence factor for pathogens yet the physiology and regulation of swarming remain poorly understood. The research proposed here constitutes the first phenotypic and genetic characterization of swarming in a Gram positive bacterium, Bacillus subtilis. Interestingly, swarming motility found in wild B. subtilis isolates is lost in domesticated laboratory strains and thus presents a novel phenotype for this well studied organism. Multicellular behavior and morphological changes associated with the phenotype will be studied in detail. B. subtilis is a robust bacterial model genetic system and the genetic determinants of the swarming phenotype will be analyzed in three ways: I) directed mutagenesis of candidate genes predicted by comparative physiology, II) random transposon mutagenesis and III) microarray-based transcriptional analysis.